What is meant by social constraints? Are constraints of any kind necessary for enjoying freedom?

a. Social Constraints are the external controls made by the society upon the individual.

b. The government is the part of society, hence it is assigned with the task to put limitation on the freedom of the citizens.

Yes, Constraints are necessary for enjoying the freedom:

a. Constraints are necessary to to develop respect for the views of others.

b. It is necessary to create an equal society.

c. Absence of constraints would lead to imposition of beliefs on others and give rise to conflicts.

Example: In Indian constitution, right to practice religious affair is a Fundamental Right and government would not intervene into, but if the practice restricts other people from following their beliefs then the government would interfere into it.